FRANKFURT — Central bankers like to portray themselves as being aloof from the hurly-burly of politics, coolly assessing the economic data as they ponder whether to add a jolt of stimulus or take some away.

But with populism on the rise in Europe and elsewhere, opinion polls have arguably become one of the European Central Bank’s most important sources of data points.

Faced with a series of national elections in which anti-euro candidates play prominent roles, Mario Draghi, the president of the central bank, mounted a spirited counteroffensive on Thursday. He portrayed the currency as the key to European prosperity and even took an implicit jab at the protectionist rhetoric of President Trump.

“Open trade has been the pillar of world prosperity for many, many years,” Mr. Draghi said.

Although it made no major changes to monetary policy on Thursday, the bank is under increasing pressure to begin withdrawing the stimulus program that has prevailed for a decade. That task, delicate in the best of times, is even more difficult in the charged political atmosphere that permeates not only Europe but also the United States and the rest of the world.

Some political candidates are questioning the whole idea of a united Europe and the European Central Bank’s fundamental reason for being. The situation raises the stakes whenever the bank makes a decision.

A wrong move by the European Central Bank could upset a fragile economic recovery and provide fodder for the populists.

While insisting that the central bank’s job is to keep inflation under control, Mr. Draghi was unusually direct on Thursday in rebutting opposition to European free trade and political unity.

“If we go back to when the euro was created, there were always people who said it’s wrong, it’s a mistake, it can’t be done,” Mr. Draghi said. “They are saying the same today.”

Eurozone members have made “extraordinary shows of solidarity” toward countries in crisis, Mr. Draghi said. “The euro is here to stay.”

No matter what Mr. Draghi does, he will continue to draw strong reactions. As one of Europe’s most powerful institutions, the central bank serves as an all-purpose piñata for nationalist politicians of all stripes.

In Italy, where low interest rates have helped ease a severe credit crunch, sentiment runs the opposite direction. When the European Central Bank does begin gradually reducing its stimulus efforts, perhaps around the middle of the year, expect leaders of the populist Five Star Movement in Italy to accuse Mr. Draghi of selling out to the Germans.

The prospect that Ms. Le Pen could become president of France has pushed up the government’s borrowing costs. The higher rates feed through to the economy and work against central bank measures intended to make sure credit remains cheap.

The political landscape in Washington is also a concern for the European Central Bank. The United States is the European Union’s largest trading partner. If Mr. Trump erects trade barriers, as he has threatened to do, European exporters would suffer along with the region’s economy.

Mr. Draghi will have his first direct contact with the new American administration next week at a summit meeting in Germany of central bank governors and finance ministers. He declined to say on Thursday what message he planned to deliver.

A further complication for the European Central Bank is that its policies are out of sync with those of the Federal Reserve. Fed officials have signaled that an interest-rate increase is likely next week. That could be a problem for the European Central Bank, if higher market interest rates in the United States spill over to the eurozone and undermine efforts to keep borrowing costs low.

Analysts say they expect the European Central Bank to give a clearer view of its intentions around June, probably by signaling a reduction in purchases of government and corporate bonds, a way of pumping money into the economy.

An increase in official interest rates may be years away. On Thursday, the European Central Bank left its benchmark interest rates unchanged, and it said it would continue the stimulus measure of buying government and corporate bonds through the end of the year, albeit at a reduced level starting in April.

However, in a statement, the central bank was less alarmist about the eurozone outlook than in the past. Mr. Draghi said the bank would not extend an emergency lending program for commercial banks because there was no need. “There is no longer that urgency in taking further actions,” he added.

It will be nearly impossible to time the easing of the stimulus in a way that does not open the European bank to criticism. The economies of the eurozone are also badly out of step with one another. Unemployment in Italy, at 11.9 percent, is three times as high as Germany’s.

The European Central Bank has already been drawn into Italian politics. The central bank, which regulates commercial lenders in the eurozone, has endorsed a rescue plan for troubled Italian banks that critics in Germany say violates European rules.

In Germany, by contrast, there are complaints that the European Central Bank’s low interest rates penalize middle-class savers, who earn almost no return on their nest eggs. The resentment has grown recently because of an increase in inflation. Consumer prices in Germany rose at an annual rate of 2.1 percent in January, above the European Central Bank’s target of just under 2 percent.

The inflation rate for the eurozone as a whole was 2 percent in February. But the increase was almost entirely because of food and fuel prices, which frequently fluctuate. The European Central Bank will probably not react until there is evidence that prices in other categories, like services, are also rising.

That may be too late for some in Germany.

“It is time for the European Central Bank to start phasing out its expansionary monetary policy in Europe,” Clemens Fuest, president of the Ifo Institute, an influential research organization in Munich, said on Thursday in a statement. “It should now take its foot off the gas.”